Interest may seem to be fading due to the lack of interesting content.
I know I look in often but see the same old arguments going on and surf away. I also see high numbers of visitors not necessarily logging on as a user. I wonder what that would mean on the graph.
As for starting new topics . . . . . come on! Arguments happen in "Recipe" threads. I wouldn't be surprised if that creates hesitation to start a topic.
There have been many recurring comments made as to the boring state of the forum and how it's not the same, missing long-time users who have moved on (some who I miss) and what the future may hold for MT.
I still say it is what it is and those interested will stay and some who will move on. I hope it will continue to change and morph thereby growing new "long time users" and perhaps drawing some MIA's to come back around. Who knows.